Sources by origin, content and intended use:
Think about how the sources were created and for what purpose
"Research literature", reports of research performed by the authors; include experiments or original observations: research articles, reports of new species, theses/dissertations, proceedings of conferences. Usually structured: introduction, materials and methods, results (tables and graphics with measurements) and discussion.
"Review literature", evaluate and discuss primary literature on a specific topic: review articles, editorials, commentaries, science books on a specific topic. Usually include historical background, present status, future developments. Many citations to primary sources.
"Basic information", present summarized versions of the other two on a specific topic: textbooks, encyclopedias, handbooks, dictionaries, documentaries, websites. Suggested as the starting point for the research process. Citations to primary and secondary sources.
Sources by Audience
Think about the target audience for your sources
Usually written by professional journalists for the general public, for entertainment, with common language and superficial content.
Written by experts in the field for students, academics and professionals, provide author’s qualifications, include citations, usually peer-reviewed, technical language, deep content.